Blue Blind

A misleading name for Tritanopia.

The name derives probably from the blue-yellow opponent channel, which is – by definition – skewed permanently to the far yellow side in Tritanopes, typically because they are missing the S-Cones that balance the channel.

“Blue blind” infers that the individual sees any shade of blue as white, black, gray, or transparent. While Tritanopes typically see violet as black, blues normally are only darkened (dark blues will appear near-black), they still perceive blues as a color, even if that color is a confusion pair with Yellow-Green. In fact, Tritanopes are more likely to see Yellow as White/Gray than Blue.

See Blue Weak.